Module 5. Building construction materials and type of building construction

Lesson 28


28.1 Introduction

Flooring requirements for different sections of dairy plant has specific needs depending on the type of sections. The flooring of process section has its typical requirement of resistance against lactic acid, alkalies and thermal shocks, this will be met by specific type of stones e.g. mandana stones. The flooring of cold store has specific requirement of non-slippery flooring with hygienic conditions to be maintained, such requirements will be met by semi vitrious tiles. The flooring of RMRD has specific requirement of good mechanical strength, resistance against the detergents, less noise problem etc. The flooring of section for fermented products like, Dahi, Cheese, Yoghurt etc., requires vitrious category of tiles to maintain hygienic conditions. Thus, flooring materials for different sections are selected based on the need of the particular section to meet sanitary standards.

28.2 General Requirement of Dairy Floors

It is necessary to use different types of the flooring material depending upon the use of the flooring surface. One single type of floor in the entire dairy plant is not possible if wear is to be kept to a minimum. Dairy floor requires different types of flooring in order to cope with hazards and other problems of various sections of a dairy plant. It is desirable that dairy floors should impervious, durable and long lasting. The material of flooring should be such that it can be cleaned easily cleaned, non-slippery and cost effective. The flooring is designed considering the effect of washing and cleaning as well as and the ability to withstand changes of temperature by provision of adequate expansion joints.

The provision of adequate fall and drains helps not only to avoid the possibility of water pools but also assists the rapid removal of milk spillage and cleaning solutions. This helps in reducing the corrosion effect to the flooring materials. Normally, the fall should not be less than 1 in 80 for effective removal of liquids. Drainage channels should be at least 15 cm from the wall and drainage channels should not be placed along side walls, as far as possible. Water seepage may cause corrosion of structural steel and weakens the flooring base or R.C.C. Fig. 28.1 shows a cross section of construction of floor.


Fig. 28.1 Floor construction

28.3 Structural Base

The structural base is usually of concrete or R.C.C. A concrete structural base may be cast as a slab directly on the ground/R.C.C. or it may be suspended slab pre-cast concrete units. It should be designed to resist all the static and dynamic stresses with provision of heavy foundation required for installation of equipments. The structural base should be made of good concrete and thoroughly compacted.

28.4 Waterproof Membrane

One of the most important features at the time of planning and designing of the dairy floor is the use of water proof membrane in the floor to prevent liquids from penetrating to the base structure. The membrane should be impervious to water, resistant to corrosion, tough enough to resist damage during repairs of the floors and support loads. All joints should be thoroughly sealed to provide a continuous membrane surface. The membrane should be laid to have falls at the base structure and be extended to some distance up the walls. The material used for the membrane must be strong and yet flexible. Acid resistant asphalt laid at least 10-12 mm thick on a layer of bitumen felt is most commonly used. The best results are obtained when the asphalt is laid in two layers with all construction joints broken, i.e. two layers don’t have their joints coinciding. Good quality bituminous roofing filled with lap joints sealed with bituminous compounds is also used. Plastic films of polyethylene, polysorbetylene and polyvinyl chloride are also used for the purpose. Properties of water proof membrane are as under.

  • Water proof membrane should be impermeable to water.
  • It should be resistant to corrosive liquids and substances.
  • It should be strong enough to support the required load.

28.4.1 Types of water proof membranes

• Plastic sheet
• Chemicals
• Asphalt or Bitumen layer in the form of a thicker layer which is applied on walls to prevent leakage of water.

28.5 Flooring Materials

Portland cement concrete is mostly commonly used as flooring material. The floors are resistant to abrasion and alkali. However, it is vulnerable to weak acids and deteriorates under the influence of milk waste.

High alumina cement concrete resists acid solution above a pH 5.0 and is favorable than plain Portland cement. However, it is attacked by weak solutions of alkali and it loses its strength and resistance to abrasion under hot moist conditions. Hence, it is not regarded as a suitable flooring material for dairy plant.

Portland cement concrete often gives good service even where milk pillage occurs provided that regular cleaning takes place to remove the milk wastes. Concrete floor shrink for several months after lying, but subsequently it expands and contracts with variations of temperature and moisture content. Such expansion and contraction may be of the order of 0.05% which may give rise to cracking or curling. Where plain concrete floors are likely to wet, joining gaps of about 12-13 mm (0.5”) width should be left open down to the waterproof membrane, and after the concrete has set, they should be filled with asphalt or other suitable joining material. The dairy floors which may be subjected to considerable attrition and abrasion, the structural base should be covered by a topping of more resistant granolithic concrete.

Granolithic concrete contains more cement than ordinary cement concrete and gives good results in dairies, although its surface can be corroded slowly by lactic acids, milk residues and acid detergents. There is no shrinkage after laying concrete tiles which is made of granolithic concrete and cured under controlled conditions. They are laid in cement mortar of ratio 1:3. The joints between 1/8 and ½ inches wide must be completely filled with the same mortar. Concrete tiles may be tinted and similarly tinted mortar should be used for the joints.

Ceramic floor tiles can be used for flooring where moderate resistance to wearing is expected. These tiles are resistant to attacks by acids and alkalis. These tiles are available in different sizes such as 6” x 6”, 9” x 4.5”, 9” x 6”, 9” x 9”, 12” x 12” etc. These tiles should be thick so as to resist impact damage. Coved tiles should be used at joints between floors and walls. The tiles should be properly laid using appropriate bedding mortar and high grade filling material.

28.5.1 Requirements of a dairy floor or characteristics of a dairy floor

  • They should be impervious, smooth and easy to clean.
  • It should be able to withstand the effect of lactic acid.
  • It should be able to resist the effect of the cleaning solution, steam or hot water.
  • It should be strong enough to withstand the effect of falling objects, cans, boxes (impact resistance)
  • It should have high resistance to abrasion (wear and tear).
  • It should have desired slope towards drains
  • In processing section, the slope should be 1:80.
  • In bottling section and RMRD, the slope should be 1:40.

28.5.2 Different types of floor

  • Cement concrete floor
  • Terrazzo floor used in offices
  • Tile floor having either natural stones or synthetic tiles
  • Metal floor
  • Grill floor

28.6 Bedding and Jointing for Tile Floors

The optimum result can be achieved by adopting most appropriate way of laying and filling the joints. The materials used for the purpose mainly depend on the type of flooring material used in different sections of a dairy plant. Some of the ways of bedding and joining the floor tiles are given below.

28.6.1 Portland cement

Portland cement mortar is most commonly used for bedding material for fixing floor tiles/stones. Portland cement mortar is resistant to alkalis, but it is attacked by acids and dairy wastes. It is necessary to take adequate care to make water tight joint.

28.6.2 Super sulfated cement

Super sulfated cement is a mixture of ground blast furnace slag, calcium sulfate and Portland cement. It requires special care during hardening after laying. It is resistant to acidic and alkalis.

28.6.3 Rubber latex cements

Rubber latex cements are available for in situ floorings and are based on polyester and epoxy resins. Unsaturated polyesters which in the presence of a catalyst, react with another resin such as styrene, are usually employed for polyester flooring. It is susceptible to attack by alkalis and therefore cannot be used in dairy plants.

28.7 Metal Tiles, Plates and Grids

Metal tiles of two main types.

1) anchor steel plates

2) cost iron metal tiles

Both types are very suitable to resist impact and abrasion in dairies. They also resist the action of alkalis but they are subject to attack by weak acids.

The anchor plate is usually 12” x 12”size made of 10 gauge steel in the form of a shallow tray of about 7/8” thickness and the wearing surface is punched to give downwardly projected twisted anchors which anchor the plate to the bedding material. For laying the anchor plates, upturned tray is filled with concrete and after inversion it is tamped into position until it is firmly embedded in the concrete.

The cast iron metal steel is made of a square or a right angled triangle, apart from the hypotenuse, the sides of each type are 12” long and the tile is about 1” thick and has a projecting foot at each corner. These tiles are bedded in cement mortar and tamped down until the feet rest firmly on the structural base, so that the stresses on the tile are transferred evenly to the structure.

Metal plates are used frequently on dispatch docks and in cold stores to provide very durable wearing surfaces over concrete flooring. Metal grids are sometimes incorporated in floor surfaces as reinforcement against abrasion and are embedded in the topping so that the upper side of the grid is flush with the floor surface.

28.7.1 Cast iron grill floor

Cast iron tiles have a hollow honey comb-like structure which gives a strong surface and has no slipperiness. This type of tiles has no problem of looseness from concrete surface. It gives less noise than metal tiles when cans are moved over it. This floor has high impact and abrasion resistance. Some time, concrete part of cast iron grill floor may be eaten away due the action of h milk or acid. .

28.7.2 Cement concrete floor

The general construction includes a structural base of RCC or concrete, a screed laid to fall, a water proof membrane, a bedding mortar and a top finishing surface or layer or a wearing surface.

28.7.3 Curing of concrete

Curing of concrete is necessary to increase the strength and water tightness as cement reacts with water at a slow rate and it then becomes hard. The aggregate then formed has no reaction but it forms a strong bond and fills in the pores. Normally the structural base is 10-15 cm thick. Concrete of dairy comprises cement to sand to aggregate in the ratio 1:3:5.

28.8 Bedding Mortar

The layer of the bedding mortar is generally kept around 2-3 cm thick. It has a ratio of cement to sand as1:3. Its function is to give attachment to the top surface.

28.9 Terrazzo Floor

It is similar to concrete floor, and is generally used in offices, labs and such other places where decorative effect is required. Before hardening the top surface, marble chips of irregular shape are fixed on the upper surface and pressure is applied so that the marble chips get embedded on the wet top surface of the cement floor. After hardening, the surface is finished smooth so that the marble chips fixed on the top give a good appearance. Colored cement may be used to impart better look. Its main limitation is that it cracks when it comes in contact with hot and cold water due to thermal expansion and contraction.

28.10 Tile Floor

Two types of tiles can be used viz. natural stone or synthetic (artificial) tiles.

28.10.1 Natural stone or kota stone

It is obtained from quarries and is then cut to the required size. They are available in different colors like red, buff, light green, brown and yellow. Acid resistant Kota stone (popularly known as Mandana stone) is also available, which can be used in the dairy industry. In order to be used in the dairy plants, the stone should have a minimum thickness of about 3 - 4 cm. They may be square or rectangular and should have a 900 angle edges. The top surface should be polished and the bottom is kept unpolished to get better gripe with bedding mortar.

28.10.2 Concrete or cement tiles/ artificial tiles

These tiles can be made by making the desirable size mould using mortar and then hydraulic pressure is applied to make it non-porous and stronger. Marble chips of different colors may also be included in this type of tiles. Cement may be high alumina cement or colored cement. The size of the tiles may be 12” x 12”, 18” x 18” etc. These tiles are cured in water for 5-7 days and subsequently laid on bedding mortar. Various types of grinders are employed for surface finish of the floor. These types of tiles are rarely used as many other verities of tiles are available.

28.11 Maintenance of Floors

The following points should be considered for the maintenance of the floor of different sections of dairy plant.

1. Regular cleaning dairy floors is essential for hygiene, safety and long life of floor.

2. All the joints should be carefully observed for any water/milk/chemical penetration through the joints. Seal the joints using cementing material, if any defect is noticed.

3. Remove milk/waste water etc. from the floor in order to cause insanitary or slippery conditions.

4. Floors soiled with oil should be cleaned by scrubbing with detergent and water.

5. Lactic acid are formed as milk sours, therefore, early removal of spilled milk is desirable.

6. Use appropriate chemicals or combination of chemicals for floor cleaning. Don’t sprinkle chemicals on the floor as it may damage the floor surface. Use mild detergent solution with low free sulphate is recommended for floor cleaning.

7. Hand scrubbing with brushes or electric scrubbing followed by rinsing with clean water is recommended.

Last modified: Thursday, 4 October 2012, 9:17 AM